Experimental study on thermal runaway characteristic and residue of Li(Ni0.8Co0.1Mn0.1)O2 lithium-ion batteries induced by overcharge

Overcharge is one of the most common triggers of thermal runaway in lithium-ion batteries. The process and mechanism of overcharging are not clarified. In particular, little research has been done on thermal runaway residues. Accident investigators require a method to identify thermal runaway residue. In this study, the thermal runaway induced by 1C (12 A) current overcharge in 12 Ah pouch Li(Ni0.8Co0.1Mn0.1)O2 lithium-ion batteries was investigated. The battery residue was disassembled. Scanning electron microscopy, X-ray diffractometry, and other analysis methods were used to investigate macro characteristics, micromorphology, and phase composition of the residue. The analysis of the residues revealed that the layered electrode adhesion was severe, the current collectors at the rupture were damaged and ejected, and copper molten beads were observed in the ejecta. Numerous fracture and breaking were observed in the residue cathode material particles, and the explanatory hypothesis was proposed. New phase C, Li2CO3, LiF, MnO, NiO, Co and Ni were found. Also, the mechanisms of the phenomena and characteristics were discussed. Accident investigators would be helped if these overcharge characteristics were widely validated.